Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare destructiveHint=true and idempotentHint=false, so the safety profile is covered structurally. The description usefully adds the no-op-on-non-running behavior, which the annotations don't convey, but says nothing about the resulting run state, whether in-flight work is discarded, or permissions required.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences, purpose front-loaded ahead of the caveat, with zero filler. Every sentence earns its place.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a single-parameter control tool with full schema coverage and annotations covering safety, this is nearly complete. The main omission is the outcome of stopping (final run status, whether results are preserved), but with no output schema that is a minor gap.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100% with a single well-documented run_id (uuid format), so the schema carries full parameter burden. The description adds no additional meaning beyond what the schema provides; baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a clear verb+resource: 'Stop an agent run.' The scope word 'agent' distinguishes it from the sibling cancelBuilderRun (builder runs), but it never explicitly names alternatives like startRun or cancelBuilderRun, so differentiation is inferred rather than stated.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The no-op condition ('if the run is not currently running') implies when the tool is meaningful, but there is no explicit when-to-use vs alternatives guidance (e.g., startRun to launch, getRun to inspect, cancelBuilderRun for builder runs). Usage is implied only.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.